100 JPBINCIPLES OF CHEMISTRY

1)0 expected that silicic anhydride, SiOfi, would bo 0. gaa liko carbonic
anhydride, whilst in reality silica is ft hard non-voktil© subttanc©!1^9
and thoroforo it may with great certainty bo considered that In this
condition it is polymeric with Si03, as on polymerisation—for instance,
when cyanogen passes into par&cyanogitj, or hydrocyanic acid into
oyanuric add (Chapter IX.)— very frequently gaseous or volatile
substances change into solid, non- volatile, and physically denser and
more complex substances,® Wo will fiwt make acti«aintanoo with free
silicon and its volatilo compounds, as substances In which the analogy
of silicon with carbon !§ shown* not only in a chemical bat also In a
physical sonso.8

lo, tlio volume of CC14«04, 8ICt,«»a,OHCl5»fll»8tHC%rtflS, of
••186, mid 8i(OC8H$)4»§01, The eomwpowling trite haw also nearly ntjwl s«|H»J<to
vohnnea; for exwapl®, CtvOOj^SV, Q&SIQ8«4L It !» t*apo«aibla to ewapw @iO« ««!
C0«» bew,uM teat* physios! stes a.w» no wWely dlffertat,

' w» But sfltea, faun «.«fl voln,tltis«8 (Moti«m) In th« hmfc of tfat *l«eW« temftss, *b*mi
8000°, SlOj b also partially voktflo at Uw U»ttip«.iraUirii fttW»**t:l to Hut teu» ol tetaul*
Ing gw (Gromw, 18BS1).

* A propovty of iukiroombhifttltm ia obmorvftbk in Uui at«m»of eMlifltt,a«tl a family
foi' int0rcomtiinatfoH| or iH'lymcvtmiUon, in nbw ftwm In tlw unmvtttnttwl l)y«1mpttrl««i
antl carbon ontnpountU in gtini-rnL In ailSc'tm <v projiPrly <if (he mmt\ imtuw !» fouiul to
bo pu,rlicutiu'Iy dttvoltn»d in silica, fcii0$, which IB not tho QAHU wills oiuiHittJe niihytlmlw,
JCljo faculty of Uiu nioloBulas «£ s»llie» fciie ewmlihiiug Utth with olli«<r jtt«lt«-»]ti)i twit!
among tttomntilvoa is os^tljiW in ttio f««rofttioa of most vaviwl 0«mix»HmJ» with hftt«%
tn tlie tetnAtioM ol liy&ra,t«» wltlt » gt^amtty &«»dftf popartlen «f watas town to
atihydnmB (siliott, in tl>« eoUoid vuvlurw of Uui hydmttj (tlio nxtento ol eoHoMs wfi fttwap
complex), to ttw formation of polymeric ttlHeracCI nlta, wfi t« many olh« p»prtt»
wW^k ivlll bo eonirfteofl in ttw wquel. Having MUM to this wnelttdftn M to th« petj'
.tttesrio elate of silioft tinoo fto your* 18BO-1800, 1 Imvo fonttfl ife to be «tmftrmc»tl hy ifo
BubnBqutml ruiwawhoB em Uio ot»nj;K)uu<3tt of Hllion, tt4idt if I luiuWw nnt, tbin vinw tuw
BOW bot'Ji vory jfcncvuHy acwptiH1),

s It WIVH only uflcr Ocrliawlt, cvml in (^wi«rtij f,n?w«)nnntly It* tl><» mtatiUdJHnhnfc f»f
tholmo Rtomtc wuij?Ut«i)f UMJ dciiii'iits (Ulmjitt-r V1I.J, Hint a trim Mi'ft «»f tint utoinio
weiglil, of silicon iui<l tif tlw (umiixwition i»f nilii'a wnn nrrivi«ii itt Irmu tli" fact {)»i( ttw
moleculoN of Bifl^, BiFj, 8i((K\.irs)4, A-g,, m-vcr rciiiftiu limn Hum SH jtuth "f ».ilii ><n,

tPlto qutiaticnt o/ if/w <»>»i/«j»fti\*;H o/ «7»>rt was l«irif| tlw nnltjcwl r*f, tfs« i«r«al, e»<ntw»
•dJotory atfttemonte In ttta htekwy ol a«lfl«e«t. In tlw lout e*«tUiry Pott, fterg nuutn, «i<3
8«lu«!ltv) (•lltiUtijiai'iliet! ssilioa foctja alumina wtd MHMS. In (,)»« b^nnfag of tlw fKwnl
.otttttoy littffeioifi te the ft»tt tltoe t«|WfH»<J ttis «yittta that «IS«. wa« wn udA, &t«|
tbo mta.ew.li of imaks «&Jti of this ftdfl, Bmwltu* dtttwrnintki tto pres«»s» of my^m hi
iflloft— Mwwly, Utttl 8 parts of ©xyf m wwe united with 7 ef silicon, Ww> c«w|)**i}.I«>ti <rf
•tliea was flwt 6Kpj»w»fl as BIG (B.M for ttw sake of ihortaima S only ww w«mi»t!m«i
wriUen Snitoatlj, A»"» Investlgatlloti la Uio ajmounl of sfllca pnwml lnery»litlltn«< nilnr^iilit
uhowafl that Uio arrwunt of osygwu In the baiwi Imm ft vwfy vwM itwtjxfftlon t^ lh«
ftiaount of oxygon in tho uUi<», and that tW§ «,Ua vftritisi from S ! J tti 1 » 8. Th«
ratio 1 : 1 in tilwi n«it with, but the majority of Ihwo rn!t«)ml§ ew rwna, OOter mwi
common min«ral« coiitftiu o, krgor pitonortion of sitiea, tho w,Ho toUram tt» «fp« rtt
tbe baew crntl the oxygon of ttio dllcn, wing «gtt^l to I « 8, o» rt»w*b0Ht»$ WMfb ft» the
xftogitw, labrftcloritaa, olIgocIawB, tak, &a Th» Wghw wtlo 1 1 8 It known fe* a wid«*ly
^ftW^lftfl ««ri«i of afttuml 8iliwte»— % ewrapk, the foltpww. Tluwu •Ulonto* In wltteh
*ho anKmnt of (fflygen In Uw bMw »e «§pl to thai to ttw »Utea ft«s termed mmM^wto / otutugh o«nflrm«>Uou of